The best practice for identifying which stage in the sales process the industry standard due-diligence should be embedded is to develop a process map as a base, work with stakeholders to understand the trigger point, and locate the stage. This practice helps to:

Develop a process map as a base: This provides a visual representation of the sales process, showing the steps, inputs, outputs, roles, and decisions involved in each stage.

Work with stakeholders to understand the trigger point: This helps to elicit feedback and insights from the stakeholders who are familiar with or affected by the sales process, and identify when or why the industry standard due-diligence is needed or required.

Locate the stage: This helps to determine where in the sales process the industry standard due-diligence should be embedded, based on the trigger point and the business logic. Reference: https://trailhead.salesforce.com/en/content/learn/modules/business-analysis-process-mapping/create-a-process-map